The present invention relates to enzyme granules suitably formulated in a detergent. Further, the present invention relates to a process for preparing the enzyme granules. Further, the present invention relates to an enzyme granule aggregate suitably formulated in a detergent and a process for preparing the same.
In many cases, various enzymes are formulated in detergents such as laundry powder detergents, powder bleaching agents and powder detergents for automatic dishwashing machines for the purpose of enhancing their detergency.
Since an enzyme exhibits its effects for the first time after dissolving in water, the enzyme has such a property that a certain amount of time is required before exhibiting its effect. Therefore, in order to optimally exhibit the performance of the enzyme, whether or not the enzyme granules have a property of quickly eluting an enzyme from enzyme granules (referred to as xe2x80x9cfast dissolubilityxe2x80x9d) is important. Especially regarding the laundry detergents, and the like, its importance is even more increasing under the present situation of the tendency of shortened washing time.
Further, in a case where the formulation to a detergent is considered, when there are insoluble remnants of the enzyme granules at the termination of washing, there arises a problem such as deposition of the insoluble remnant components to washing items. Therefore, it is important that all of the substances constituting the enzyme granules are dispersed within a washing period, thereby preventing to have insoluble remnants.
In addition, in order to secure safety of the working environment, it is important to suppress the amount of powdery dusts generated from the enzyme granules (referred to as xe2x80x9camount of dusts generatedxe2x80x9d).
Further, in a case where after-blending to the detergent is considered, it is desired that the enzyme granules are homogeneously distributed in the detergent from the viewpoint of quality. In order to achieve this, it is important to prevent the classification of the enzyme granules with other granules constituting the detergent by approximating the particle size and the bulk density of the enzyme granules to those of the other granules. In addition, in consideration of external appearance, the larger the particle size, the more desirable, from the viewpoint of the visual confirmability, and the lower the bulk density, the more desirable, from the viewpoint of the number of granules.
In consideration of these viewpoints, there is becoming increasingly important a technique satisfying the fast dissolubility and the low dust generating property, properties required regardless of being formulated in a detergent composition, and also being capable of controlling a particle size and a bulk density, properties becoming important when formulated in a detergent, to match those of the detergent.
However, these properties are closely related to each other. For instance, while the dissolubility is improved by making the particle size small, the amount of dusts generated tends to increase at the same time. While the amount of dusts generated is lowered by increasing the bulk density, the dissolubility tends to be lowered at the same time. Therefore, it has been conventionally difficult to obtain enzyme granules satisfying these required properties at the same time.
For instance, Japanese Examined Patent Publication No. Sho 50-22506 discloses a process for preparing a microcapsule comprising an enzyme for detergents, comprising spray-drying a solution comprising the enzyme for detergents and an inorganic salt being copresent in a water-soluble binder solution, or a dispersion thereof. While the microcapsule actually prepared which has a particle size in a range of from 20 to 130 xcexcm can be thought to satisfy excellent dissolubility when formulated in a detergent to be used, it is difficult to suppress the classification phenomenon caused among the granules, because the particle size is extremely small as compared to the detergent. In addition, in the enzyme granules obtainable by this technique, since the content of the water-soluble substance is substantially large, the enzyme granules have a hollow structure having a weak strength, so that it is difficult to suppress the amount of dusts generated, and thereby the required properties described above for an enzyme could not be satisfied at the same time.
Japanese Patent Laid-Open No. Hei 7-289259 discloses a process for preparing enzyme granules for detergents, comprising subjecting a mixture comprising an enzyme for detergents and aluminosilicate powder to agitation and tumbling granulation using a water-soluble organic binder.
According to this process, a problem regarding the suppression of the amount of dusts generated is solved by carrying out granulation. However, it is difficult to satisfy the fast dissolubility owing to an increase in the particle size and the compression of the granules during granulation, and thereby the required properties described above for an enzyme could not be satisfied at the same time even by this process.
An object of the present invention is to provide enzyme granules in which an enzyme is rapidly eluted, without insoluble remnants, and the generation of the powdery dusts is suppressed, thereby having a property such that classification phenomenon generated among the granules in the detergent composition is less likely to take place (referred to as xe2x80x9cnon-classifiable propertyxe2x80x9d), in a case where the enzyme granules are formulated in a detergent together with other components. A further object of the present invention is to provide a process for preparing the enzyme granules. A still another object is to provide an enzyme granule aggregate in which an enzyme is rapidly eluted, without insoluble remnants, and the generation of the powdery dusts is suppressed, thereby having a non-classifiable property, in a case where the enzyme granules are formulated in a detergent together with other components, by aggregating enzyme granules having structure such that more amount of a water-soluble binder is present near the surface of the enzyme granules than the inner portion thereof. A still another object is to provide a process capable of suitably preparing an enzyme granule aggregate. These objects and other objects of the present invention will be apparent from the following description.
Specifically, the present invention relates to:
[1] enzyme granules comprising (A) a water-insoluble substance and/or a slightly water-soluble substance; (B) a water-soluble binder; and (C) an enzyme, wherein the content of (A) component is 45% by weight or more, and wherein the enzyme granules have an average particle size of from 150 to 500 xcexcm and a bulk density of from 500 to 1,000 g/L, and have a structure such that more amount of (B) component is present near the surface of the enzyme granules than in the inner portion thereof;
[2] a process for preparing the enzyme granules of item
[1], comprising spray-drying a slurry comprising (A) a water-insoluble substance and/or a slightly water-soluble substance; (B) a water-soluble binder; and (C) an enzyme at a temperature so as not to substantially deactivate the enzyme, to give the enzyme granules;
[3] an enzyme granule aggregate comprising enzyme granules comprising (A) a water-insoluble substance and/or a slightly water-soluble substance; (B) a water-soluble binder; and (C) an enzyme, wherein the enzyme granules have a structure such that more amount of (B) component is present near the surface of the enzyme granules than in the inner portion thereof; and
[4] a process for preparing an enzyme granule aggregate, comprising adding water or an aqueous binder solution to enzyme granules, drying and/or cooling the resulting mixture, the enzyme granules comprising (A) a water-insoluble substance and/or a slightly water-soluble substance; (B) a water-soluble binder; and (C) an enzyme, wherein the enzyme granules have a structure such that more amount of (B) component is present near the surface of the enzyme granules than in the inner portion thereof; or comprising adding a molten thermoplastic binder to the enzyme granules and cooling the resulting mixture, thereby giving the enzyme granule aggregate.